ABSTRACT / SUMMARY

An exper iment i s conduc ted to p repare soap and thus , to

compare the p roper t ies o f the p repared soap and syn the t i c

de te rgen ts wh ich a re p rec ip i ta t ion , emu ls i f i ca t ion and c lean ing

ab i l i t i es . I t can be conc luded tha t soap has the p roper t ies o f

emu ls i f y ing o i l whereas de te rgen t has no t . The ab i l i t i es o f fo rming

p rec ip i ta tes can be seen c lear l y in soap so lu t ion whereas de te rgen t

fo rms no p rec ip i ta tes a t a l l . The exper iment i s comple ted and

success fu l l y conduc ted .

INTRODUCTION

The mak ing o f soap was be l ieved to be f i r s t i nven ted by the

Baby lon ians in 2800 BC and the Phoen ic ians a round 600 BC. In the

ear l y h is to ry , soap was used fo r the purpose o f c lean ing tex t i l e

f i b res such as woo l and co t ton in p repara t ion fo r the dye ing p rocess

ins tead o f persona l hyg iene . Our ances to rs f rom o ld days f igu red ou t

the layer o f g rease on garments wh ich w i l l obs t ruc t the app l i ca t ion

fo r the dye ing p rocess .

Soap was named a f te r Mount Sapo, accord ing to a Roman

legend , was a p lace where the Romans per fo rmed a r i tua l o f an ima l

sacr i f i c ing . I ron ica l l y , the fa ts o f the an ima ls tha t go t m ixed w i th

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wood ashes was then washed downh i l l where the women d iscovered

tha t the mix tu re a ided the i r c lo th wash ing ac t i v i t i es .

Eugène Chevreu l was the person respons ib le fo r the found ing

o f chemica l na tu re o f soap and the modern soap-mak ing begun in the

19 t h Cen tu ry .

In today ’s p rogress ive wor ld o f sc ience and techno logy , soap i s

manufac tu red much l i ke i t was back then , where fa ts and o i l s a re

techn ica l l y hea ted w i th the p resence o f a s t rong base (common ly

sod ium hydrox ide o r po tass ium hydrox ide) to p roduce fa t t y ac id sa l t s

and g lycero l i n a p rocess te rmed as sapon i f i ca t ion . As a mat te r o f

fac t , the sa l t o f a fa t t y ac id i s the soap , wh ich i s a so f t and waxy

mate r ia l tha t b rush up the ab i l i t y fo r c lean ing purpose o f wa te r . A

pos i t i ve ion , usua l l y Na + o r K + , and a nega t i ve ion usua l l y the an ions

o f long-cha ined carboxy l i c ac ids y ie lded by hydro lys is o f e i the r

an ima ls o r vege tab les fa ts .

The p resence o f doub le bonds (unsa tu ra ted) w i th fa t t y ac ids

mate r ia ls , o r soap tends to decrease i t s me l t ing po in t and thus , the

compounds a re in l i qu id s ta te a t room tempera tu re . Techn ica l l y ,

vege tab le fa ts a re re la t i ve ly unsa tu ra ted and l i qu id under the

o rd inary cond i t ions , whereas an ima ls fa ts a re re la t i ve ly more

sa tu ra ted and so l id o r semi -so l id a t the same tempera tu re . Doub le

bonds a re sa id to lower the me l t ing po in t o f a fa t t y ac id cha in

because i t s c i s -con fo rmat ion p roduces a ben t cha in wh ich does no t

eas i l y adhere to a ne ighbour ing cha in by a Van der Waa ls a t t rac t ion .

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Hence a lower tempera tu re i s requ i red fo r these mater ia ls to fo rm a

so l id c rys ta l l a t t i ce .

However , dur ing Wor ld War 1 , the f i r s t syn the t i c de te rgen t has

been p roduced , ma in ly because o f the u rge to f ind ano ther c lean ing

agen t tha t wou ld reac t in hard wate r .

A var ie ty o f de te rgen ts can be found today , wh ich genera l l y

con ta in sur fac tan ts , a bu i lde r , and o ther add i t i ves such as b leach ing

agen ts and enzymes. The sur fac tan ts a re the par ts tha t a re

respons ib le fo r the c lean ing p roper t ies o f tha t par t i cu la r de te rgen t .

Some o f them may be ion ic , ca t ion ic o r even non- ion ic . The bu i lde rs

indeed a re compounds respons ib le fo r remov ing the cor respond ing

ca lc ium and magnes ium ions in hard wate r .

However , the re a re two de te rgen ts wh ich may no t be as sa fe as

i t may concern , mos t l y tha t con ta ins phosphates . Such de te rgen ts

w i l l end up in was tewate r and cause excess ive g rowth o f a lgae and

o ther aqua t i c p lan ts . When those d ie , bac te r ia tha t p resen t in the

dead mat te r consume oxygen wh ich resu l t s in the lack o f oxygen le f t

fo r the f i sh and o ther aqua t i c l i ves .

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AIMS / OBJECTIVES

The purposes o f conduc t ing th is exper iment a re to p repare

soap w i th us ing minera l o i l s and to s tudy and compare the p roper t ies

o f soap and syn the t i c de te rgen t .

THEORY

I f R-COOH represen ts a genera l i sed fa t t y ac id (R i s

hydrocarbon cha in o f 13 , 15 o r 17 Carbon) then , the genera l fo rmu la

fo r a fa t i s :

A genera l i zed sapon i f i ca t ion reac t ion i s shown be low:

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The par t i cu la r s t ruc tu re o f the soap mo lecu le cons is ts o f a long

non-po la r ta i l ( the hydrocarbon cha in o f the fa t t y ac id ) and a h igh ly

po la r end ( the ion ic g roup COO - ) . The non-po la r s i te , o r a lso ca l led

as hydrophob ic ta i l i s ab le to d isso lve the g rease and d i r t whereas

the po la r o r hydroph i l i c end i s a t t rac ted to wa te r mo lecu les .

The non-po la r por t ion o f the soap i s common ly represen ted

wi th a z ig -zag l i ne and the po la r head w i th a c i rc le .

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non-polar

polar

A mice l le , a spher ica l shape i s fo rmed resu l t ing f rom the

nega t i ve ly charged heads o f the soap mo lecu les . They then o r ien t

themse lves , where the non-po la r ta i l s rear range towards the cen t re

o f the mice l le and the hydroph i l i c s i te fac ing the wate r . In the

p resence o f o i l o r d i r t , the non-po la r head in te rac t w i th them, and

ga thered i t to the cen t re o f the mice l le . Th is i s how soap c leans

techn ica l l y . When r insed w i th wa te r , the mice l le toge ther w i th the

d i r t washed away . Soap i s theore t i ca l l y ac t ing as an emuls i f y ing

agen t , where emu ls ion i s the d ispers ion o f a l i qu id in a second

immisc ib le l i qu id .

In ac id ic o r hard wate r , the soap mo lecu les wou ld no t be ab le

to in te rac t w i th wa te r , m ice l les can hard ly be fo rmed and thus , soap

can no longer be ab le to per fo rm i t s c lean ing ab i l i t i es . The COO -

g roup i s l i t e ra l l y p ro tona ted and the fa t t y ac id p rec ip i ta tes , be ing

now wate r inso lub le . Hard wate r i s wa te r wh ich i s h igh ly

concen t ra ted w i th Mg o r Ca and these ions reac t w i th the carboxy l

and fo rming inso lub le fa ts o r sc ien t i f i ca l l y known as scum, and

resu l t s in the inab i l i t y o f the soap to c lean .

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water

APPARATUS

~s tock soap so lu t ion , d is t i l l ed wate r , syn the t i c de te rgen t (dynamo) ,

m inera l o i l s , CaCl 2 so lu t ion , MgCl 2 so lu t ion , FeCl 2 so lu t ion , 1 M HCl ,

tomato sauce , pH meter , tes t tubes w i th racks , beakers , and c lo th

s t r ips .

EXPERIMENTAL PROCEDURE

Par t A : Soap p repara t ion

1 . 25 mL o f vege tab le o i l i s p laced in a 250-mL Er lenmeyer f l ask . 20

mL o f e thano l and 25 mL o f 6 M sod ium hydrox ide so lu t ion a re added

to the f lask . The mix tu re i s s t i r red us ing a s t i r r ing bar to m ix the

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con ten ts o f the f lask . The a lcoho l i s ca re fu l l y sme l led by waf t ing i t

towards our nose .

2 . The 250-mL f lask i s hea ted in a 600 mL bo i l i ng -wate r ba th .

3 . The mix tu re i s s t i r red con t inuous ly dur ing the hea t ing p rocess to

p reven t the mix tu re f rom foaming . I f the mix tu re shou ld foam to the

po in t o f near l y over f low ing , the f lask i s removed f rom the bo i l i ng -

wate r ba th un t i l t he foaming subs ides , then hea t ing i s con t inued . The

mix tu re i s hea ted fo r 20-30 minu te o r un t i l t he a lcoho l odor i s no

longer de tec tab le .

4 . The pas te - l i ke m ix tu re i s removed f rom the wate r ba th and the

f lask i s coo led in an i ce ba th fo r 10-15 minu tes .

5 . Wh i le the f lask i s coo l ing , the vacuum f i l t ra t ion appara tus i s

assembled as shown in the f igu re be low. The vacuum f lask i s

secured to a r ing s tand w i th a u t i l i t y c lamp to p reven t the appara tus

f rom topp l ing over .

6 . A p iece o f f i l t e r paper i s we ighed to the neares t 0 .001 g and the

mass i s recorded . The f i l t e r paper i s p laced ins ide the Buchner

funne l . The paper i s mo is tened w i th wa te r so tha t i t f i t s f l ush in the

bo t tom o f the funne l .

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7. Once the f lask has coo led , 150 mL o f sa tu ra ted sod ium ch lo r ide

(NaCl ) so lu t ion i s added to the f lask to "sa l t ou t " the soap .

8 . The wate r a t the asp i ra to r i s s low ly tu rned on . The mix tu re f rom

the f lask i s poured in to the Buchner funne l . Once a l l o f the l i qu id has

f i l t e red th rough the funne l , the soap was washed w i th 10 mL o f i ce -

co ld wate r . The suc t ion f i l t ra t ion i s con t inued un t i l a l l o f the wate r i s

removed f rom the soap .

9 . The soap i s removed f rom the funne l and p ressed be tween two

paper towe ls to d ry i t . The f i l t e r paper and d r ied soap a re we ighed ,

and the mass i s recorded to the neares t 0 .001 g and the mass o f the

soap de te rmined by d i f fe rence and the mass i s then recorded .

Par t B : Compar ison o f soap and de te rgen t p roper t ies - p rec ip i ta t ion

and emuls i f i ca t ion .

1 . A s tock soap so lu t ion i s p repared by d isso lv ing 2g o f the p repared

soap in 100 mL o f bo i l i ng , d is t i l l ed wate r . The mix tu re i s s t i r red un t i l

t he soap has d isso lved and the so lu t ion i s a l lowed to coo l .

2 . S tep 1 i s repea ted us ing 2 g o f syn the t i c de te rgen t . When bo th

so lu t ions a re coo l , the pH o f each so lu t ion i s de te rmined us ing pH

paper .

3 . Three tes t tubes a re labe led as tes t tube 1 , 2 , and 3 . 4 d rops o f

m inera l o i l a re added to each tes t tube . 5 mL o f d is t i l l ed wate r i s

added to tes t tube 1 . 5 mL o f s tock soap so lu t ion i s added to tes t

tube 2 . 5 mL o f s tock syn the t i c de te rgen t i s added to tes t tube 3 .

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4. Each so lu t ion i s m ixed by shak ing and le t s tand fo r th ree to f i ve

m inu tes . The so lu t ions , i f any , tha t emu ls i f i es the o i l by fo rming a

s ing le layer i s no ted .

5 . The mix tu res a re poured in to the Waste Conta iner . The th ree tes t

tubes a re c leaned and d r ied .

6 . Three more tes t tubes a re labe led as tes t tube 1 , 2 , and 3 . 2 mL

o f s tock soap so lu t ion i s p laced in each o f the th ree tes t tubes . 2 mL

o f 1% CaCl2 so lu t ion i s added to tes t tube 1 . 2 mL o f 1% MgCl2

so lu t ion i s added to tes t tube 2 . 2 mL o f l% FeCl2 so lu t ion i s added

to tes t tube 3 . Each tes t tube i s shaken to m ix the so lu t ions . The

observa t ions a re recorded .

7 . 4 d rops o f m inera l o i l a re added to each o f the tes t tubes in S tep

6 . Each tes t tube i s shaken to m ix the so lu t ions and the so lu t ions

a re le f t to s tand fo r th ree f i ve m inu tes . The so lu t ions , i f any , tha t

emu ls i f i es the o i l by fo rming a s ing le layer i s no ted .

8 . S teps 6 -7 i s repea ted us ing 2 mL o f s tock de te rgen t so lu t ion . The

so lu t ions tha t p rec ip i ta ted a re observed .

9 . The so lu t ions , i f any , tha t emu ls i f i es the o i l by fo rming a s ing le

layer i s no ted .

10 . The mix tu res a re poured in to the Waste Conta iner . The tes t tube

a re c leaned and d r ied .

11 . 5 m l o f s tock soap so lu t ion i s poured in c ine c lean tes t tube and

5 mL o f s tock de te rgen t so lu t ion in a second tes t tube . 1 M HC1 is

added one d rop a t a t ime to bo th so lu t ions un t i l t he pH in each tes t

tube i s equa l to 3 . The number o f d rops o f ac id added to each

mix tu re i s coun ted . Any p rec ip i ta te fo rmed in e i ther m ix tu re i s

observed .

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12. 1 d rop o f m inera l o i l i s added to each tes t tube in S tep 11 . Each

tes t tube i s shaken to m ix the so lu t ion . Any emuls i f i ca t ion fo rmed in

e i ther m ix tu re i s observed .

Par t C : Compar ison o f c lean ing ab i l i t i es o f soap and de te rgen ts

1 . The th ree beakers a re c leaned , d r ied and labe led . Then 20 mL o f

s tock soap so lu t ion ( f rom Step 1 in sec t ion 7 .4 .2 ) i s p laced in the

f i r s t beaker . A f te r tha t , 20 mL o f s tock de te rgen t so lu t ion ( f rom Step

2 in Par t B ) i s p laced in the 2nd beaker . 20 mL o f a commerc ia l

l i qu id i s added in a th i rd beaker .

2 . Three c lo th tes t s t r ips tha t have been soaked in tomato sauce a re

ob ta ined and then one s t r ip i s p laced in each o f the beakers .

Repeated ly each so lu t ion i s s t i r red w i th a s t i r re r bar fo r 5 m inu tes .

3 . The c lo th s t r ips i s removed f rom the soap and de te rgen t so lu t ion

and then the excess wate r i s squeezed ou t . Each c lo th s t r ip i s

observed and compared to de te rmine the i r re la t i ve c lean l iness .

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RESULTS

i)

Mass o f f i l t e r (g ) 0 .3698

Mass o f f i l t e r paper + soap +

con ta iner (g )

140 .0688

Mass o f soap recovered (g ) 56 .5872

Mass o f con ta iner (g ) 83 .1118

i i ) pH o f soap so lu t ion : 10 .06

pH o f de te rgen t so lu t ion : 8 .61

i i i )

Tes t tube Observa t ions

4 d rops o f o i l + 5mL o f

d is t i l l ed wate r

o i l d rop le ts fo rmed

4 d rops o f o i l + 5mL o f

soap so lu t ion

o i l d i sso lves in so lu t ion

4 d rops o f o i l + 5mL o f

de te rgen t so lu t ion

very t iny o i l d rop le ts and

bubb les fo rmed

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i v )

Tes t tube Observa t ions

2mL o f de te rgen t + 2mL o f

1% CaCl 2

c lear so lu t ion i s fo rmed

2mL o f de te rgen t + 2mL o f

1% MgCl 2

Clear so lu t ion i s fo rmed

2mL o f de te rgen t + 2mL o f

1% FeCl 2

Clear so lu t ion i s fo rmed

v)

Tes t tube Observa t ions

2mL o f soap so lu t ion + 2mL

o f 1% CaCl 2

Scum is fo rmed bu t d isperse

in so lu t ion

2mL o f soap so lu t ion + 2mL

o f 1% MgCl 2

Whi te scum is fo rmed

2mL o f soap so lu t ion + 2mL

o f 1% FeCl 2

Yel low ish scum is fo rmed

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v i )

Tes t tube Number o f d rops

5mL o f soap so lu t ion 8 (p rec ip i ta te i s fo rmed)

5mL o f de te rgen t so lu t ion 11

v i i )

Mate r ia l C lean ing ab i l i t i es

Soap Clean

Dete rgen t C lean fas te r

DISCUSSION

I n sapon i f i ca t ion , the fa t t y ac id carboxy la te ions a re fo rmed in

the p resence o f the base . These carboxy la te ions a re the con juga te

bases o f the fa t t y ac ids , and there fo re , ab le to accep t a p ro ton .

When p laced in to wate r , these con juga te bases a re ab le to accep t

p ro tons f rom any source inc lud ing wate r .

Water tha t con ta ins ca lc ium ions , Ca 2 + , and magnes ium ions ,

Mg 2 + , i s sa id to be hard wate r . These ions a re leached f rom ground

wate r f l ow ing over rock fo rmat ions con ta in ing l imes tone and o ther

m inera ls . Hard wate r in te r fe res w i th the c lean ing ac t ion o f soaps .

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When soap i s added to hard wate r , i nso lub le compounds a re

fo rmed wh ich appear as s t i cky scum. Th is scum leaves a depos i t on

c lo thes , sk in , and ha i r . However , when bo i led , hard wate r leaves a

depos i t o f ca lc ium carbona te , CaCO 3 . Th is sca le bu i lds up in tea

ke t t les and ins ide ho t wa te r hea te rs .

Dete rgen ts have unden iab ly rep laced soap fo r many c lean ing

jobs a round the home. The deve lopment o f syn the t i c de te rgen ts by

chemis ts was a g rea t advan tage fo r peop le w i th re la t i ve ly hard tap

wate r in the i r homes.

However , the re i s a s ign i f i can t i ssue regard ing the use o f

syn the t i c de te rgen t tha t i s the b iodegradab i l i t y o f some o f i t s

components . In fac t , many o f the sur fac tan ts in i t i a l l y used in

de te rgen ts were no t b iodegradab le whereas soaps a re

b iodegradab le , apparen t l y can be degraded by bac te r ia .

F rom the observa t ions ob ta ined f rom th is exper iment , the soap

f rom prec ip i ta tes in a l l o f the so lu t ions added (CaCl 2 , MgCl 2 and

FeCl 2 ) as we l l emu ls i f i es the o i l . Th is may no t appear as good

charac te r i s t i c fo r soap as a c lean ing agen t i f i t f o rms p rec ip i ta te and

emuls i f i es o i l on c lo th .

Never the less , de te rgen t i s a be t te r c lean ing agen t as i t fo rms

no p rec ip i ta t ion and does no t emu ls i f i es the o i l . Thus , g rease and

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d i r t can be c leaned w i thou t invo lv ing any p rec ip i ta t ion o r o i l

emu ls i f i ca t ion .

CONCLUSION

The soap i s success fu l l y p repared and the compar ison o f

p roper t ies o f soap and de te rgen t , wh ich a re p rec ip i ta t ion ,

emu ls i f i ca t ion and c lean ing ab i l i t i es , a re made and observed .

I t can be conc luded tha t soap has the p roper t ies o f emu ls i f y ing

o i l whereas de te rgen t has no t . The ab i l i t i es o f fo rming p rec ip i ta tes

can be seen c lear l y in soap so lu t ion whereas de te rgen t fo rms no

p rec ip i ta tes a t a l l .

RECOMMENDATIONS

There a re a few recommendat ions tha t w i l l s ign i f i can t l y p roduce

be t te r observa t ions wh ich w i l l no t dev ia te much f rom the theore t i ca l

observa t ions .

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F i rs t l y , the exper iment shou ld a t leas t be repea ted tw ice in

o rder to ge t more accura te observa t ions . The observa t ions migh t be

more conv inc ing i f the average i s taken .

Second ly , any pH read ing mus t be conduc ted a t same

tempera tu re fo r pH i s va ry ing a t d i f fe ren t tempera tu res .

Avo id con tac t w i th any chemica l reagen ts invo lved . Thus , wash

hands be fo re leav ing the labora to ry .

REFERENCES

1. Exper iments in Genera l Chemis t ry Fea tu r ing Measur ing Net ,

Bobby Shanton , L in Zhu , C .H. A twood, 2005 , Brooks /Co le

Labora to ry Ser ies , USA.

2 . Organ ic Chemis t ry ( th i rd ed i t ion ) , R . T . Mor r i son & R. N .

Boyd ,1973 , A l l yn and Bacon , Bos ton .

3 . Fundamenta ls o f Genera l , Organ ic and B io log ica l Chemis t ry

( th i rd ed i t ion ) , J . McMur ry , M.E . Cas te l l i on , 1999 , Pren t i ce

Ha l l , Inc . Upper Sadd le R iver , New Jersey .

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APPENDICES

~ Refe r to the a t tachments p rov ided on the nex t page .

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